The invention is directed to electrostatic spraying, and in particular, to a nozzle for electrostatic spraying.
Dairy barns and other buildings where livestock are kept provide ideal breeding grounds for the common house fly. Very large populations of this pest can develop and thus, pose a sanitary problem. This necessitates the periodic spraying of these buildings to control the fly population with insecticides. For adequate fly control it has been found that the periodic application of residual pesticides is necessary.
At present, residual sprays are sprayed mechanically often by hand using a manually pressurized tank which is carried around the building during the application. This method of spraying insecticides in barns or other livestock operations has been often reported as ineffective or unsatisfactory, particularly for the hard to reach areas in barn ceilings where breeding centers for flies develop. The sprays or aerosols generated by means of hand or mechanically operated apparatus do not deposit easily on critical locations for the control of flies. For an adequate coverage of all areas, unnecessarily large amounts of pesticides may have to be used.
With the large amount of pesticide which must be used, the farmer may be exposed to the pesticide he is spraying and the animals in the barn may be exposed to insecticide which drips into the bedding or feed. If the coverage is inadequate in some areas however, it may allow resistance to the insecticide to build up in fly populations.
It is well known, as documented in the text by N. A. Fuchs, "The Mechanics of Aerosols", Macmillan, New York, 1964, pp 102-103, that an electrostatically charged aerosol cloud will expand continuously while retaining its general shape. This is due to the mutual repulsion between each of the particles and all other particles in the cloud. If the cloud is in a contained space, a supplementary phenomenon intervenes which further helps the deposition of the aerosol particles over the entire inside surface of the enclosure. In addition to being repelled by each of the other particles, each particle is also attracted by its electrostatic image charge in the surrounding surfaces. Such image charge varies in location and time depending on the conductivity and permittivity of the enclosing walls.
A paper by I. I. Inculet entitled "Electrostatic Charging and Dissipation of Dust Clouds in Enclosed Rooms" and published in the IEEE Transactions on Industry and General Applications, March/April 1971, gives the results of experiments which demonstrate the effectiveness of dissipation of aerosols by electrostatic forces. In U.S. patent application Ser. No. 305,438, filed Sept. 25, 1981, by Ion I. Inculet, and now abandoned, a method and apparatus are described for spraying electrostatic clouds which include different spray materials in distinct portions of the cloud. Such a system would allow the upper portion of a barn to be sprayed with insecticide while the lower portion is sprayed with water.
The spraying apparatus illustrated in the above patent application, however, is particularly suited for spraying clouds outdoors, such as in orchards or other large agricultural areas.